1. Field of the Invention
The present invention relates to a wing structure. More particularly, the present invention relates to a single piece composite wing structure.
2. Technical Background
The design of aircraft wings poses difficult design problems. Multiple factors must be balanced in order to design an effective wing. One consideration is the shape of the wing. The wing must have the proper airfoil-shape in order to create the desired lift. The flying surface of the wing must be such that it does not disturb the aerodynamic flow of air. The wing must also have enough strength to lift the weight of the aircraft fuselage. Furthermore, many aircraft wings also serve as a fuel tank, which adds complexity to the design of the wing. Compounding the difficult design parameters is the desire to make the wing as light-weight as possible.
Aircraft wings are commonly comprised of a flying surface and various structural members. The structural members may include spars and ribs that intersect with one another within the wing. Together, the spars and ribs transfer the lift from the flying surface to the fuselage of the aircraft. The spars and ribs are often made of a machined metal, such as aluminum, that is manufactured to precise tolerances and load requirements. The flying surface of the wing may also be a metal that is attached to the structural members to define the airfoil of the wing.
Attaching the flying surface to the structural members typically includes creating thousands of holes in the flying surface and the structural members. Thousands of rivets are then needed and are often manually placed in each hole. The process of creating thousands of holes in the wing and inserting thousands of rivets in the holes substantially increases the manufacturing cost of the wing. Additionally each hole in the wing weakens the flying surface and the structural members. Furthermore, by increasing the number of parts for a wing, the chances of introducing a defective part are correspondingly increased. Another drawback to current wing designs is the weight increase caused by the numerous fasteners and bulky metal structural members.
Recently, composite materials have been introduced as a desirable material for aircraft structures. Composite materials are often comprised of strands of fibers, typically carbon fiber, mixed with a resin. The fibers are often wound or woven into a sheet of material and then impregnated with a resin. The composite material is then formed into the desired shape and cured until properly hardened. Composite materials have the advantage of being extremely light weight and having high strength. Additionally, composite structures are easily molded into desired shapes and configurations.
Unfortunately, there are several drawbacks to composite materials. First, composite materials are very expensive. This high cost is a result of the cost of the raw materials as well as the cost of manufacturing the composite parts from the raw material. The high manufacturing costs of the composite structures combined with the price of the expensive raw materials, often makes the use of composite materials cost prohibitive.
Another drawback to composite materials is the assembling of the composite material. Different considerations must be made for assembling composite materials than with other materials. Placing holes in composite materials for attachment of fasteners, severs the strands of fibers within the material and creates weak points within the material. While forming holes in the composite material by displacing the strands of the uncured fiber prevents severing of the fibers, this process is time-consuming and often impractical.
Another alternative for assembling composite materials is the use of high strength epoxies. Epoxies have the advantage of limiting the number of manufacturing steps. However, the distribution of the epoxy and the placement of the parts together can require expensive machines and numerous jigs.
Regardless of whether composite materials or traditional metals are used in the wing, an inspection of each fastener attachment must be performed. Obviously, the more fasteners and attachments in the wing, the more inspection will be required. Not only must these fasteners and attachments be inspected after manufacturing, they must also be periodically inspected throughout the life of the aircraft. Thus, the construction of the wing has implications not only on the initial cost of the wing, but also implications on the maintenance costs through the life of the wing.
Therefore, there is a need in the art for a wing that limits the number of fasteners present in the wing. There is also a need for a wing that may be assembled with limited assembly procedures. There is a further need for a wing that is light weight. A need also exists for a wing that limits the extent of inspection required in post manufacturing and during maintenance. A need further exists for a low-cost composite wing. Such a wing and method for manufacturing the wing are disclosed and claimed herein.